tracing, x86/irq: Do not trace arch_local_{*,irq_*}() functions

I triggered a triple fault with gcc 4.5.1 because it did not
honor the inline annotation to arch_local_save_flags() function
and that function was added to the pool of functions traced by
the function tracer.

When preempt_schedule() called arch_local_save_flags() (called
by irqs_disabled()), it was traced, but the first thing the
function tracer does is disable preemption. When it enables
preemption, the NEED_RESCHED flag will not have been cleared and
the preemption check will trigger the call to preempt_schedule()
again.

Although the dynamic function tracer crashed immediately, the
static version of the function tracer (CONFIG_DYNAMIC_FTRACE is
not set) actually was able to show where the problem was.

 swapper-1       3.N.. 103885us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103886us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103886us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103887us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103887us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103888us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103888us : arch_local_save_flags <-preempt_schedule

It went on for a while before it triple faulted with a corrupted
stack.

The arch_local_save_flags and arch_local_irq_* functions should
not be traced. Even though they are marked as inline, gcc may
still make them a function and enable tracing of them.

The simple solution is to just mark them as notrace. I had to
add the <linux/types.h> for this file to include the notrace
tag.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110702033852.733414762@goodmis.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/include/asm/irqflags.h b/arch/x86/include/asm/irqflags.h
index 5745ce8..bba3cf8 100644 (file)
--- a/arch/x86/include/asm/irqflags.h
+++ b/arch/x86/include/asm/irqflags.h
@@ -60,23 +60,24 @@ static inline void native_halt(void)
 #include <asm/paravirt.h>
 #else
 #ifndef __ASSEMBLY__
+#include <linux/types.h>
 
-static inline unsigned long arch_local_save_flags(void)
+static inline notrace unsigned long arch_local_save_flags(void)
 {
        return native_save_fl();
 }
 
-static inline void arch_local_irq_restore(unsigned long flags)
+static inline notrace void arch_local_irq_restore(unsigned long flags)
 {
        native_restore_fl(flags);
 }
 
-static inline void arch_local_irq_disable(void)
+static inline notrace void arch_local_irq_disable(void)
 {
        native_irq_disable();
 }
 
-static inline void arch_local_irq_enable(void)
+static inline notrace void arch_local_irq_enable(void)
 {
        native_irq_enable();
 }
@@ -102,7 +103,7 @@ static inline void halt(void)
 /*
  * For spinlocks, etc:
  */
-static inline unsigned long arch_local_irq_save(void)
+static inline notrace unsigned long arch_local_irq_save(void)
 {
        unsigned long flags = arch_local_save_flags();
        arch_local_irq_disable();